Laboratory air handling unit

ABSTRACT

The invention is an air handling system that is shared between a laboratory and offices within the same building. The normally separate office and lab systems have been combined by way of an air return system that draws air from the offices and feeds into both the office and lab air supplies. The re-circulation of the office air draws more fresh outside air into and lessens requirements for the heating and cooling systems for the offices.

TECHNICAL FIELD

[0001] The present invention relates to air handling systems forbuildings and more specifically for buildings with space allocated forboth laboratory and general office use.

BACKGROUND

[0002] The ventilating systems for general purpose buildings typicallycomfort condition, and then recirculate most of the air within thebuilding, only discharging a small percentage of the air to the outsideenvironment. The ventilating objectives for a laboratory are verydifferent. Because chemicals or biological substances employed in labwork often emit harmful or otherwise undesirable fumes, the ventilationsystem for a laboratory typically comfort conditions the air and thenexhausts the air to the environment without any recirculation so thatthe fumes do not diffuse within the building. To enable technicians toexperiment with fume emitting chemicals or biological substances whileavoiding human contact therewith, one or more fume hoods are used. Fumehoods provide an area in which technicians can work without the risk ofinhaling dangerous fumes. The work area is contained within a vacuumwhich draws and expels the toxic air from the lab to the outside of thebuilding.

[0003] Special heating, ventilating, and cooling problems arise when alaboratory and offices share a common building. Currently, thelaboratory and offices are served by separate air handling units.Separate units have been required because of the above-noted differentventilating objectives. But, the use of separate air handling units isinefficient and compromises office air quality.

[0004] Inefficiency is caused by the closed system requirements of theprior art laboratory air handler. Because the laboratory air handler isnot allowed to recirculate air, 100% of the air is drawn from outsidethe building. In contrast, most office handling units draw only 10% ofair from outside the building and recirculate the rest. Even though mostof the outside air drawn by the laboratory air handling system will soonbe exhausted due to the large air flow demands of the fume hood, all ofthe air must still be treated for comfort (i.e., cooled, dehumidified,warmed) so that the laboratory will be desirably environed.Consequently, the operating cost of the laboratory air handling unit canbe 5 to 10 times more per floor area unit than that of the office airhandling unit. Thus, the overall building efficiency is lowered.

[0005] Besides being inefficient, the prior art systems also compromiseair quality in the office sections of the building. Fresh air isdesirable in work environments. Prior art laboratory air handlers arerequired to draw 100% outside air for safety considerations, thus thereare no stale air concerns. Prior art office air handling units, however,bring in 10% or less outside fresh air. Thus, in the prior art airhandling systems, the laboratory ends up being fresh air “rich,” and theoffice fresh air “poor.”

[0006] Because of the above efficiency and air quality considerations,there is a need for an air handling system that would reduce the outsideair treatment burden on the laboratory air handling system and at thesame time deliver more outside air to the offices.

SUMMARY OF THE INVENTION

[0007] The present invention solves the above problems by using aLaboratory Air Handling Unit (LAHU), which is a common air handlingsystem for both the laboratory and the offices, instead of the prior artseparate systems. The LAHU design links the laboratory and office airhandling systems with an air return system which draws air from theoffice and recirculates the air to both the laboratory and/or office airsupply systems. The use of the return system serves to overcome theefficiency and office air quality problems associated with theseparately operating prior art air handlers.

[0008] The foregoing and other advantages, features, and objects of thisinvention will become more apparent from the following detaileddescription which reference the accompanying drawings in which:

[0009]FIG. 1 is a schematic representation of the LAHU for a buildingcontaining both laboratory and office space;

[0010]FIG. 2 is a structural representation of the LAHU.

DETAILED DESCRIPTION

[0011] The prior art efficiency problems are overcome by an air returnsystem. Outside air needs to be treated for comfort by the office supplysystem, whereas air returned from the office does not because it hasalready been treated. When the air flow in the laboratory is greaterthan that in the office (e.g., when a fume hood is in use), the returnair from the office is mixed with outside air and used to modulate theair drawn into the laboratory to maintain a set-point. Because thelaboratory fume hood air consumption needs are partially met by themixed recirculated air from the office, less outside air is needed.Because less outside air is needed, the burden on the air treatmentsystems (ie., heaters, preheaters, cooling coils) for the laboratory isgreatly reduced. The reduction in air treating requirements for thelaboratory system increases the overall efficiency of the building.Therefore, the LAHU eliminates the efficiency deficits created by theseparate office/lab prior art systems by linking the two with a returnair system.

[0012] The return air system also solves the prior art office airquality problems. The typical prior art office air handler draws 10% orless air from outside the building. However, the LAHU causes the officeto draw in much more fresh air. More fresh air is drawn because thereturn air system, by evacuating air from the office to the more needylaboratory air handling system, creates an air volume deficit in theoffice which is satisfied by drawing in additional outside air. When theairflow of the laboratory section is lower than the airflow into theoffice section, the laboratory section receives 100% return air from theoffice section. Because the return system of the LAHU draws more freshair into the office, the prior art air quality problems are eliminated.

[0013] Referring now to the drawings, schematic FIG. 1 and structuraldrawing FIG. 2 depict the LAHU a building according to the presentinvention. The building contains an office area 1 and a laboratory area2. The office area 1 is served by an office supply system 50 and thelaboratory 2 is served by a laboratory air supply system 60.

[0014] The building typically has a common outside air source 48. Theoutside air temperatures are measured by both an insertion-type-wet-bulbair temperature sensor 11 and an insertion-type-dry-bulb air temperaturesensor 12 respectively. Before passing into the buildings heating,ventilating and cooling (HVAC) systems, the outside air passes through afilter 9 across which a pressure difference is measured by an airpressure differential sensor 13 in a manner known in the art. The air isthen optionally acted on by a heat recovery unit 10 after which airtemperature is sensed by a cross-over-type-dry-bulb air temperaturesensor 14. The building has only one outside air source 48.

[0015] Outside air 48 may be optionally be drawn by both the officesupply system 50 and the laboratory supply system 60 if threshold vent52 is open (as is typical when the system is in operation). The officesupply system 50 has its own climate control system having both apreheating coils 4 and cooling coils 5. Temperature readings upstreamand downstream of both sets of coils 4, 5 are recorded by threecross-over-type-air-temperature sensors 15, 16, 17 and used to controlthe preheater 4 and cooling coils 5 in a manner well known in the art.Pressure differences upstream and downstream of the preheating coils 4are measured by a air pressure differential sensor 18 used to controlthe airflow through the preheating 4 and cooling coils 5. Furtherupstream of the climate control system, a fan 3 is used to direct airinto the office area. Before entering the office area, temperature andpressure are sensed by an insertion-type-dry-bulb-air-temperature sensor19 and pressure sensor 20 respectively. Aninsertion-type-dry-bulb-air-temperature sensor is also maintained withinthe office. The temperature sensors in the outside 19 and inside 49 theoffice cooperate with the preheating 4 and cooling coils 5 to maintaindesirable temperatures in the office area 1. The pressure sensor is usedto control fan 3 speed. Some of the air supplied to the office isexhausted naturally to outside the building in an uncontrolled manner21.

[0016] The laboratory supply system 60 also has a threshold vent 52 andutilizes a climate control system functionally identical to that servingthe office, having preheating coils 7, cooling coils 8, threecross-over-type-dry-bulb-air-temperature sensors 22, 23, 24, and apressure differential sensor reading across the preheating coils 7. Thelaboratory supply system 60 also has a fan 6 to move the air into thelaboratory. Immediately upstream of the fan 6 is across-over-type-air-temperature sensor 26, a carbon dioxide sensor 27,and an airflow-rate sensor 28. Downstream of the fan 6, the air pressure29 and dry-bulb temperature 30 are sensed by sensors 29, 30 before theair is propelled into the laboratory 2 by the fan 6. The carbon dioxidesensor 27 is used to monitor system air freshness and regulate systemventilation to optimize the same. The fan 6 speed is variably controlledbased on readings from the pressure sensor 29. Aninsertion-type-dry-bulb-air-temperature sensor 31 is also maintained inthe laboratory 2. The temperature sensors outside 30 and inside 31 theoffice are used to control the laboratory preheating 7 and cooling coils8 to maintain desirable temperatures in the laboratory 2. As withoffices, the laboratory also naturally exhausts some air to the outsidein an uncontrolled fashion 32. However, the laboratory also has one ormore fume hoods 33 which can exhaust large quantities of air from theoffice when activated, and minimal air when the fume hood is not in use.

[0017] Fume hoods 33 may comprise a fan 34, temperature sensor 35, andheat recovery unit 36 in a manner known in the art. The use of the fumehood dramatically drops the pressure in the laboratory 2. This pressuredrop is sensed by the pressure sensor immediately upstream of thelaboratory 29 which electrically and mechanically causes the an increasein fan 6 speed. This dramatically increases the demands on thelaboratory supply system 60 in terms of both air volume and climatecontrol. Prior art systems handled these increased demands by merelydrawing more air through the laboratory supply system threshold vent 62.However, the LAHU handles these increased demands by linking the officeand laboratory systems to share the burden.

[0018] The LAHU office supply 50 and laboratory supply 60 systems areoptionally linked by a vented duct 37 which joins the office andlaboratory supply systems (when the vent 38 is open) between the climatecontrols and the office 3 and laboratory 6 supply air fans. This linkageallows the laboratory to draw treated air from both the office airsupply system 50, thus reducing the burden on the laboratory preheating7 and cooling 8 coils by transferring that burden to the officepreheating 4 and cooling 5 coils.

[0019] The present invention also links the two systems by providing areturn air system 39 which is capable of recirculating air from theoffice to both the office and laboratory supply systems. The return airsystem draws air from the office with a return air fan 39. The speeds ofthis fan are controlled using pressure and air flow rates as detected bypressure 40 and airflow 41 sensors immediately downstream from the fanin cooperation with the pressures sensed in the office 20 and the laband the airflow measured into the lab by the other airflow sensor 28.This enables air to be drawn from the office to be recirculated to thelaboratory air handling system 60. The return air system also contains arelease vent to the outside 70.

[0020] The return air may be recirculated to three different systemlocations. First, the return air may be tapped into the office supplysystem upstream of the office climate control systems at junction 42 byopening a first vent 45. Second, the return air may be tapped into thelaboratory supply system upstream of the laboratory climate controls atsecond junction 43 by opening a second vent 46. Finally, the return airmay be tapped into the laboratory supply system immediately downstreamof the laboratory climate controls at a third junction 44 by opening athird vent 47. The return air may be tapped in at one two or all threelocations depending on whether particular vents are open or closed.

[0021] The opening of the first vent 45 only results in the LAHUoperating in the manner of prior art handlers in that air is merelyrecirculated to the office. When either the second 46 or third vents 47are opened, the air returned by the office is shared with the laboratorysupply system causing the desired efficiency aspects of applicant'sinvention. Air admitted at the second junction 43 results in the returnair mixing with the outside air drawn by the needy office air supplysystem 60 (when the fume hood 33 is open) upstream from the laboratorypreheating 7 and cooling coils 8. Air admitted at the third junction 44is mixed with air already treated. The air mixture at either pointrelieves much of the burden on the laboratory climate control systemsbecause the temperature differential across the preheating 7 and coolingcoils 8 will be reduced because the air upstream and downstream thereofis modulated by the return air. The second 46, third 47 or both ventsshould be open to create this desired effect.

[0022] This modulation by recirculation of the air by linking the officeand laboratory systems dramatically increases the overall heating andcooling efficiency for the building. Outside air must be climatecontrolled, whereas air returned from the office does not because it hasalready been treated. Because air flow in the laboratory is greater thanthat in the office when a fume hood is in use, the second 46 and third47 vents are normally opened and the return air from the office is mixedwith outside air and used to modulate the air drawn into the laboratoryto maintain a set-point. Because the laboratory fume hood airconsumption needs are partially met by the mixed recirculated air fromthe office, less outside air is needed. Because less outside air 48 isneeded, the burdens on the climate controls for the laboratory 7, 8 aregreatly reduced. Because the reduction in burden on the laboratoryclimate controls 7, 8 is greater than the increased burden on the officeclimate controls 4, 5, overall building efficiency is increased. Thisimproved efficiency has been shown to result in annual energy savingsfrom $0.30 to $1.20 per square foot of floor area.

[0023] The return air system also provides exceptional air quality inthe office. Typical prior art office air handlers draw 10% or less airfrom outside the building. However, the newly invented system causes theoffice to draw in much more fresh air. When a fume hood 33 is inoperation, both threshold vents 52, 62 are open. Fresh air intake intothe office air supply system is stepped up because some of the officereturn air is being drawn through second 46 and third 47 vents by theneedy laboratory air handling system. The air that is recirculated fromthe office to the laboratory is replaced by fresh air from outside thebuilding through the office air supply system 50 raising the fresh airpercentage to well above the 10% prior art level. Likewise, when theairflow of the laboratory section is lower than the airflow into theoffice section, threshold vent 62 is closed and the laboratory sectiondraws 100% of the return air from the office section. In either case,the result is the replacement of stale office air with fresh outside airup to several times more than is allowed by prior art systems.

[0024] In addition to optimizing efficiency and air quality, the newlyinvented air handler saves space and costs less to produce. Because itworks more efficiently, cooling coils and preheating coils can be 20%smaller than for prior art systems. Further, some of its reheat coilscan be eliminated because of the air return system. These structuralreductions are doubly beneficial. First, they reduce the overallmechanical space required to house the air handler. The LAHU is 20%smaller than prior art air handling systems. Second, the LAHU is muchless expensive to produce. The construction cost of the LAHU is 15%lower than a prior art separate office/laboratory air handlers.

[0025] The LAHU air handler is also versatile, in that by closing offvents 38, 46 and 47, the office and laboratory supply systems may beoperated separately without returning any air from the office to thelaboratory—just like the prior art systems.

[0026] Variations and modifications of the above described system willundoubtedly suggest themselves to those skilled in the art. Accordingly,the foregoing description should be taken as only illustrative ratherthan having any limiting effect on the following claims.

1. An air handling unit for use in a building having an office area anda laboratory area, the air handling unit comprising: an office airsupply system which draws air from outside the building; a laboratoryair supply system which draws air from outside the building; an airreturn system which draws air from the office area for re-circulationthrough at least the laboratory air supply system.
 2. The air handlingunit of claim 1 wherein the office air supply system comprises a fan, apressure sensor, and an air flow rate sensor.
 3. The air handling unitof claim 1 wherein the laboratory air supply system comprises a fan, apressure sensor, and an air flow rate sensor.
 4. The air handling unitof claim 1 wherein the air return system comprises a fan, a pressuresensor, and an air flow rate sensor.
 5. The air handling unit of claim 1wherein the office and laboratory air supply systems each havepreheating and cooling systems.
 6. The air handling unit of claim 5wherein the re-circulated air feeds into the laboratory air supplysystem upstream of the laboratory preheating and cooling systems.
 7. Theair handling unit of claim 6 wherein the re-circulated air also feedsinto the laboratory air supply system downstream of the laboratorypreheating and cooling systems.
 8. The air handling unit of claim 7wherein the re-circulated air also feeds into the office air supplysystem upstream of the preheating and cooling systems.
 9. The airhandling unit of claim 5 wherein the re-circulated air feeds into thelaboratory air supply system downstream of the laboratory preheating andcooling systems.
 10. The air handling unit of claim 9 wherein there-circulated air also feeds into the office air supply system upstreamof the office preheating and cooling systems.
 11. The air handling unitof claim 5 wherein the re-circulated air feeds into the office airsupply system upstream of the preheating and cooling systems.
 12. Theair handling unit of claim 5 wherein the office and laboratorypreheating systems each comprise preheating coils, temperature sensors,and an air pressure differential sensor, and the office and laboratorycooling systems each comprise cooling coils and temperature sensors. 13.The air handling unit of claim 5 having a vented duct cross linking theoffice and laboratory air supply systems immediately downstream of thepreheating and cooling coils of each system.
 14. The air handling unitof claim 1 wherein the laboratory has a fume hood therein.
 15. A methodof handling air for use in an a building having both an office sectionand a laboratory section comprising the steps of: supplying outside airto the office section using an office supply system; supplying outsideair to the laboratory section using a laboratory supply system; andrecirculating air from the office section by feeding at least thelaboratory supply system.
 16. The method of claim 15 including theadditional step of the laboratory receiving 100% return air from theoffice section when the airflow is lower than the airflow of the officesection.
 17. The method of claim 15 including the additional step ofeither heating or cooling the air in both the office and laboratorysupply systems depending on a sensed temperatures within each system.18. The method of claim 17 including the additional step of using thereturn air from the office to modulate the supply air temperatures ofboth the office and laboratory sections by mixing the return air withthe outside air supplied to the office and laboratory supply systems.19. The method of claim 17 including the additional step of crosslinking the office and laboratory supply systems immediately downstreamfrom the location in each system that the air is heated or cooled. 20.The method of claim 15 including the additional step of recirculatingsome of the air from the office to the office supply system.
 21. Themethod of claim 15 with the additional step of operating a fume hood inthe laboratory section.